a. Field of the Invention
This invention relates to fastener assemblies. In particular, the invention relates to a lock washer for releasably locking a fastener to an object and a method for releasably locking a fastener to an object.
b. Background Art
Over time, fasteners used in many applications can become loose due to vibration, temperature changes, the failure to properly torque the fastener and other factors. The use of multiple fasteners can provide some measure of safety relative to the loosening of any one fastener. Oftentimes, however, an application does not permit the use of multiple fasteners. As a result, a variety of mechanisms have been developed to limit or prevent loosening of fasteners. For example, a cotter pin is often used to secure the position of a fastener relative to a castle nut or similar structure. The use of cotter pins, however, requires specialized fastener components (e.g., cross-drilled holes in bolts) and is labor intensive thereby adding significant costs and delays in assembly. Various flat, split and formed lock washers have also been developed that are designed to apply a force against a bolt head or nut which is overcome as the fastener is torqued down. These lock washers apply a constant force against the fastener that is relatively low to enable the fastener to be torqued down and may therefore be insufficient to prevent loosening of the fastener in certain applications. U.S. Pat. No. 4,938,644 discloses a locking assembly including a specially formed collar that is disposed about the shank of a hex head fastener. The collar is biased against the head of the fastener by a spring and may be disengaged from the head by applying a force to extensions on either side of the collar to overcome the force of the spring. The locking assembly has several drawbacks, however, including the need for multiple components and modifications to the fastener.
The inventor herein has recognized a need for a lock washer for releasably locking a fastener to an object and a method for releasably locking a fastener to an object that will minimize and/or eliminate one or more of the above-identified deficiencies.